Abstract Nickel selenides have grasped extensive attention in the field of electrocatalysts for the energy -storage and -conversion applications due to their diverse stoichiometry phases being beneficial for designing and… Click to show full abstract
Abstract Nickel selenides have grasped extensive attention in the field of electrocatalysts for the energy -storage and -conversion applications due to their diverse stoichiometry phases being beneficial for designing and tailoring a unique chemical state. The comprehensive electrocatalytic understanding of nickel selenides possessing a scenario of more than one phase requires special attention for exploiting novel bifunctional electrocatalytic activity. In this report, we propose and develop two series of in-situ grown nickel selenide phases, NiSe2 and Ni0.95Se, supported on nickel foam (NSNF) as a bifunctional electrocatalyst for alkaline water electrolysis applications. The NSNF with a well-controlled uniform particle growth orientation provides a favorable active catalytic surface to deliver an exceptional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a 1 M of KOH electrolyte solution. The half-cell performance of the optimized NSNF electrode has been demonstrated to possess the following characteristics: In the HER evaluation, the achieved overpotential values of 175, 276, and 338 mV for 10, 50, and 200 mAcm−2, respectively; In the OER evaluation, the observed overpotential value of 325 mV at 50 mA cm−2 which outperformed the state-of-the-art IrO2 catalyst. Moreover, the alkaline water electrolysis cell demonstration using the optimized NSNF electrocatalyst as a bifunctional electrode exhibits an energy efficiency of 79% as well as a steady alkaline water-splitting process of 17 h at a current density of 50 mAcm−2. The insightful understanding of the bifunctional NSNF electrocatalysts asserts their potential use in the alkaline water electrolyzer applications.
               
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